Multisensor node using Ceech board

Here are some pics of my multisensor node, using the Ceech board with lithium battery charger. The stripboard houses - from left to right - a BMP180, HTU21D and BH1750FVI. As you can see, I've soldered radio and connections directly to the board, to reduce height in order to fit the box.

@Dwalt I cut a slot in one end of the box; I intend to use it outdoors, mounted vertically, so that the slot is at the bottom.
The button is a reset button, wired to the RESET connection on the Ceech board. I made a small hole in the lid (covered with Sellotape!), so that I can insert a pin / paper clip to press it.

I had similar problems with solar panels: battery didn't seem to be charging. Also, you're getting a high solar voltage (6.64V) on a sunny day, as I did. I was concerned, as the absolute max Vin for the LTC4067 - from the datasheet, if I remember correctly - is 6.2V.

I gave up using solar cells, and I'll just charge the battery from a USB charger when I need to.

I think the key here is in the potentiomenters, so I looked around for some guidance:

The two trimmer potentiometers are used to determine the current for both the input side - to better match the internal resistance of the solar cell - and for the battery charge current. At shipping they are both set to around half the value ( 2.5kOhm), which set both currents to about 75mA.

I don't know how to measure the internal resistance of the solar cell (shouldn't be as simple as measuring it with a ohmmeter, right?), but I'm assuming that if 75mA is half the value, the maximum should be 150mA. Since my panels in parallel can supply (theoretically) up to 200mA, I'll rotate the potentiomenter to its maximum. Now, wich potentiomenter is it (not identified in the board), and what to tune in the other potentiometer (should be the same mA, what does it depend on)?

@joaoabs Try lowering input voltage. The IC is in overvoltage mode and we don't want to damage it. Next, try with 5V input. See if you get the charge.
The trimmer potentiometers:
The left one is battery charge current limit. Turn it to the left in order to maximize charging current.
And the right one is input current limit. Keep the input current below solar panel maximum current. Turn it left to increase current limit.

This is a formula to calculate input current: Ilim = 200V/Rclprog , where Rclprog stands for trimmer resistance.
And this is how you calculate charging current: Ich = 1000V/Rprog, where Rprog stands for trimmer resistance. It is also limited with input current.

~CHRG is at ADC A7. It pulls low when the battery is getting charged. It's not always zero, sometimes is stuck around 10 or below. It works in conjunction with ADC A6, which is a battery current pin. Do you get any reports here?

Ah, yes. I think i know what the problem is. The LTC4079 has a built-in MPPT power tracking for solar panels and won't charge if the input voltage is below set point. This helps optimizing power extraction from solar panels. If you are using 5V input, then you should adjust the trimmer pot on the board. Like this
Turn the top round part of the trimmer to the left so that the wiper reaches 5V mark like on the above picture. In other words reduce trimmer resistance to minimum. The other way around is for 18V solar panels.

This is a one turn trimmer. Its minimum value is close to 5V mark on one of the above pictures. And its maximum value is next to 18V mark. Since you've turned it more than once, you have to first determine the current wiper position. If you look closely you can see that the turning top is not quite round. One side is a bit flattened. That is the opposite side of the wiper. Now if you take a look at your picture then I think your wiper position is at around 6 or 7V ( to use the same terminology). I would say 20 more degrees to the left and you'll reach 5V.

You can also measure the trimmer's resistance. Like so
Find the minimum value between marked points. That is your target resistance value.